The airplane wing provides the majority of the lift an airplane requires for flight. Its shape is specifically designed for the aircraft to which it is attached. On most aircraft, the interior of the wing is also used to store the fuel required to power the engines
The primary function of the airplane wing skin is to form an impermeable surface for supporting the aerodynamic pressure distribution from which the lifting capability of the wing is derived. These aerodynamic forces are transmitted in turn to the ribs and stringers by the skin through plate and membrane action. Resistance to shear and torsional loads is supplied by shear stresses developed in the skin and spar webs, while axial and bending loads are reacted by the combined action of skin and stringers
Although the thin skin is efficient for resisting shear and tensile loads, it buckles under comparatively low compressive loads. Rather than increase the skin thickness and suffer a consequent weight penalty, stringers are attached to the skin and ribs, thereby dividing the skin into small panels and increasing the buckling and failing stresses. This stabilizing action of the stringers on the skin is, in fact, reciprocated to some extent although the effect normal to the surface of the skin is minimal. Stringers rely chiefly on rib attachments for preventing column action in this direction.We have noted in the previous paragraph the combined action of stringers and skin in resisting axial and bending loads.
The role of spar webs in developing shear stresses to resist shear and torsional loads has been mentioned previously; they perform a secondary but significant function in stabilizing, with the skin, the spar flanges or caps which are therefore capable of supporting large compressive loads from axial and bending effects. In turn, spar webs exert a stabilizing influence on the skin in a similar manner to the stringers.